I'm trying to come up with an Excel formula that shows the require volume growth we would need to see from a customer, after we give them a discount, that will generate the same margin.

For example, lets assume we have a customer that buys $1,000 worth of product in a month and has a margin of 20%. If we offer him a concession like free freight on all his orders, and we assume that concession costs 5%, the new margin from that customer is now 15%. I'm looking for the formula that shows that instead of $1,000 in revenue, we now need to get $1,333.33 in revenue to generate the same $200 in profit.

Attached is the spreadsheet I'm working with. I'm trying to show, for customers of various margins, how much incremental volume we would need to get to pay for each of the concessions. I feel like this should be simple, but I can't figure it out. I'd prefer to use a native formula, but i'm open to a macro or custom function that uses the goal seek feature...

Cost-of-Concessions.xlsx
=1/((C$2+$B3)/C$2)

Thomas